Pinewood Derby Car on E-bay

[Gavin Chafin]

I typed "Pinewood Derby" into E-bay and was checking out some cars. This guy is selling this really nice-looking car:

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... gory=19015

The guy put a lot of effort into it and, at first glance, it looks to be a super car. There's been 11 bids and the price is $65 with over a day left. Does anyone see the problem with the car?

[Colibri]

The wheels might not be fully mounted yet

[Darin McGrew]

The phrase "unclear on the concept" comes to mind...

[terryep]

Re: ebay car. Nice paint job but I like to have the block reversed so that the center of mass is higher up the start ramp. (it's wheels are too far forward). Also, I can't tell if too much of the tread surface has been removed. Is the tread bead still on the wheel? Many rules require this bead to be visible.

Terry

[Da Graphite Kid]

You're right Gavin - this is a really nice looking car. I don't see a thing wrong with how it is built other than he put the flame decals on the wrong end... he's got them so they will face backwards when he races it! I understand why he may have made the front end swoop up like it does (slow manually operated start gate) but not why the back end is lower.

'Course if it was me that built it, I would have used the slots closest to the end of the block for the rear wheels instead of the front like he did!

Da Graphite Kid

[Gavin Chafin]

Re: ebay car. Nice paint job but I like to have the block reversed so that the center of mass is higher up the start ramp. (it's wheels are too far forward).

Yes, that's my observation. For such a nice car, it such a silly mistake.

[gpraceman]

Does anyone see the problem with the car?

What's this a new game... spot the design flaw?

I'm really suprised there would be a market for finished cars. If someone likes collecting them that is one thing, but to try to pass it off as their own or their kid's

[Gavin Chafin]

What's this a new game... spot the design flaw?

But it's such a fun game! For last year’s Pinewood Derby, my brother-in-law (who works on Corvettes) said that he wanted to build a car for my son (not with him, but for him). He figured that since he can work on Corvettes that he could build a super-fast PWD car. I said, “Go ahead. But if our car is faster, we’re using our car.” He didn’t have a clue what he was doing and I figured there was no way he could build a fast car. Well, he traced out a crude pattern of a Corvette (in all of 30 seconds), had a buddy take another 60 seconds to cut it out, and then handed it to me and said he was too busy to finish it. The first thing I noticed was that he used the wrong axle slots (front and rear reversed). I thanked him, but didn’t even touch the car. He has probably mentioned that car at least 5 times and said that we could’ve won the District race if we used it. He says, “You should study the design of that car. I think you could’ve learned something.” What a bonehead.

[Darin McGrew]

I'm really suprised there would be a market for finished cars.

Yep. I've had inquiries about whether a couple of my cars were for sale, but that was different--people wanted to buy them as art objects, not as finished derby cars ready for racing.

[stefjeano]

Why would anyone pay that kind of money for a car! I thought the idea of a Pinewood Derby was to build the car with your child. There is enough info on the internet to build your own car for less than $10. It is easy to build a winner!

[Da Graphite Kid]

Why would anyone pay that kind of money for a car! I thought the idea of a Pinewood Derby was to build the car with your child. There is enough info on the internet to build your own car for less than $10. It is easy to build a winner!

If you build a pinewood derby car with your son or teach him how to build his own - than you are both winners.

Da Graphite Kid

[Colibri]

Ok someone explain what’s going on. I think the car looks fine. Pointy end down with flames, and swoopy end to the back. It looks like they used the standard slots from the block. It has a nice slim block. I don’t know where the weight has been added so I don’t know where the center of mass is. What am I missing?

[Stan Pope]

Ok someone explain what’s going on. ... What am I missing?

It appears that the CM is limited to being too far forward because the short end of the block was selected as the "front." So, its engineering doesn't measure up to its finish.

On the axle insertion depth... some of us set 'em up that way on purpose! With the new BSA kits, we have to slice 1/8" off the side in order to do it, tho.

[Colibri]

It appears that the CM is limited to being too far forward because the short end of the block was selected as the "front." So, its engineering doesn't measure up to its finish.

Ok I still don’t get it. How do you know where that center of mass is? If someone uses the slots that are in the block, does this mean that one needs to use the slot with the longer distance at the front, and what does that do for the car?

You guys have to realize that I’m just starting in this thing, so I might have a lot of questions.

[Stan Pope]

It appears that the CM is limited to being too far forward because the short end of the block was selected as the "front." So, its engineering doesn't measure up to its finish.

Ok I still don’t get it. How do you know where that center of mass is? If someone uses the slots that are in the block, does this mean that one needs to use the slot with the longer distance at the front, and what does that do for the car?

You guys have to realize that I’m just starting in this thing, so I might have a lot of questions.

Oops! Did I say where the CM is? Or, did I say where the CM could be ("is limited to")?

On the usual 28 ft. start line to finish line tracks with initial slope of 30 degrees leveling out at floor level after about 12 feet, the CM should be as far back as stability allows. (Your homework is to figure out why this is true.)

Stability is more than not "popping a wheelie." It includes hugging the track and not finishing the last few feet with a "death rattle." Longer tracks and slicker tracks require more weight on the front wheels than a "good old wooden Piantedosi," which likes about an ounce on the front
wheel.

That help?